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Someone's shooting at my plane out of the blue! What do I do?
Let us assume that you are in cruise flight in normal, civil-accessible airspace (i.e. not any sort of restricted, prohibited, warning, controlled firing, or other specialized airspace area used for firing containment or security reasons) on an IFR flight plan and in contact with the appropriate ATC agency.  Suddenly, without any warning, notice, or provocation, you see tracers whizzing by your plane!  Assuming you are taking appropriate evasive maneuvers, how do you communicate your situation and your responses to ATC in an unambiguous way? What do you squawk?  7500? 7700?  How does this change for air-to-air fire vs ground-to-air fire?
Furthermore, what evasive maneuvers could a civil aircraft reasonably perform in response to a) air-to-air and b) ground-to-air fire?  Or are you better off not trying to evade fire?

If you're already in contact with ATC, saying "Mayday" is guaranteed to get their attention. Squawking 7700 makes doubly sure.

@GregHewgill -- good point on that -- edited the Q to specify that we not only need to get their attention, but communicate our situation in an unambiguous way...

Plain English is generally best for unambiguous communication when things are going wrong.

@RalphJ -- even with a foreign controller of questionable English proficiency? (not saying all are -- there are some real embarrassments among native speakers on the radio, and some controllers in far-off lands are quite sharp when it comes to English I'm sure -- but standardized phraseology also exists for a reason)

May I politely suggest you fly the airplane before doing anything else? Evasive action might be a good idea.

@egid -- I kind of glossed over that originally, but expanded on it now

One of my co-workers at a previous job was shot at with a hunting bow by an irate hunter. The hunter missed. He was low enough (legal under our FAA waiver) that being hit was a possibility, but unlikely. This was in Class G, and definitely not IFR. I recall the pilot reported the incident to police, possibly after landing.

Why would you squawk 7500? You're not being hijacked... If you are experiencing air-to-air fire in a GA airplane, you've violated some kind of military airspace and have ignored repeated, explicit directions from a big grey bird and ATC.

If your controller won't understand "I'm being fired upon" in English & you can't speak his language either, then ATC may not be a particularly useful resource for you that day! Might try calling the attacker on Guard. No standard phraseology I know of for "tell whoever is shooting at me that you haven't told me about so far (thanks a lot!) to cease fire, please." Hastily improvised defensive maneuvering might work, but complying with an interceptor's instructions might have better odds of survival.

Given analysis of active shooter situations on the ground where running away in a straight line is typically the best way of evading (as opposed to a zig-zag run), I would expect that flight directly away from a ground shooter would be the best defense here.

@RonBeyer -- you'd hope that'd be true the world round re: only taking air-to-air fire if you've violated military airspace and ignored the ensuing intercept, but sadly, that's not something that is guaranteed.

What exactly are you asking? You want to communicate with ATC, but under the assumption that they are unable to understand you? That's a bit of a paradox, and not really a clear question. There is no standard phraseology for a situation like this, so you have to use common sense and clear language - just like you would in any other unusual situation not covered by standard phraseology.

Roll in hot and then come around and strafe!

Here is an instance where such a thing happened -- https://en.wikipedia.org/wiki/2001_Peru_shootdown

For my answer I'm going to assume that someone is genuinely trying to shoot you down for some reason, it's not some sort of legal intercept. If you ignore a legal intercept then I can see a warning shot being fired to get your attention, in which case I would tell ATC I've been intercepted and get on guard (121.5) and communicate with them and follow their instructions, evasive maneuvering in this case is a bad idea. I'm also assuming that no missiles are involved because if you are against a missile equipped enemy in a PA-28 the missile's going to win. It may be called a Warrior but let's face it, it ain't.
In the incredibly unlikely event that someone is trying to kill you without warning then communication with the ground would be my last priority in the situation you describe because ATC cannot help you and you don't have time to explain it to them anyway. If you have a one-button squawk emergency button by all means hit it, but first and foremost you need to keep positive control on the airplane. If you exceed your critical AOA and end up in a spin you are in a worse emergency and if you rip the wings off you are dead.
If it is at night then turning off your lights would be a smart idea, this won't help if the fire is radar guided but it will if the fire is visual. If there's a cloud very close by going into it is probably a great idea.
Next you need to determine whether the fire is air or ground based. If it's ground based you will know because the tracers will be going from below you to above you (hopefully not through you) then your best bet is to throttle up and clear the area as quickly as you can by staying on the same track so you get away from the guns. Diving will increase your airspeed allowing you to clear the area faster but keep it below the vne! Some small left/right turns may help to throw of the aim of the guns, but large turns will only serve to keep you close to the guns for longer. If there's terrain nearby which you can put between you and the guns then use it.
If the fire is air based then the tracers will be closer to the horizontal. If you are being shot at from another aircraft then flying in a straight line is likely the worst possible idea, you need to maneuver. If your airplane is faster than theirs then dive and outrun them, but chances are you aren't going to be able to do that, so personally I would corkscrew down and cling to the nap of the earth. Use your short turning radius to its best effect and don't fly a predictable path. Ideally I would use terrain and/or clouds to try and break visual contact so I can escape.
If you can spare a few cycles in all this you should make a mayday call to ATC and tell them you're being shot at, and whether it is another aircraft or someone on the ground. Say your intentions, your aircraft condition, and the number of people on board. This isn't likely to immediately help you, but it may help to keep someone else from flying into the same situation if there's a nutcase on the loose with an anti-aircraft gun or someone's strapped a 50 cal to their SR-22 and is playing red baron with passing aircraft. If you're lucky local law enforcement or the military may be able to scramble something fast and take the heat off you, but most likely it's all over by the time they get there.

I agree with most of this except the cloud recommendations. You are going to be distracted already, maintaining control, especially for a VFR pilot, is going to be next to impossible. For ground fire, the best thing you can do is climb. Bullets from most civilian guns aren't very effective at more than 2000' and will probably bounce off even at 5000' if they get that high. Assuming you're getting shot at by some irate landowner for flying too low, the best thing you can do is climb out and notify ATC or authorities when you land.

In my answer I'm assuming you are being shot at my more than an irate farmer with a 12 gauge, by the time you realize you're being shot at you'd be out of range anyway. As for the cloud bit, the question says you are on IFR, I'm assuming an instrument pilot and equipped aircraft. At that point you'd have to think which risk is greater, going into cloud or being peppered by shrapnel. All good points though.

This is one reason why even non-IFR-rated pilots should practice cloud flying at every opportunity.  If I have at least a working turn-and-bank indicator, I'll take my chances with clouds over bullets.


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Why do the RNAV (GPS) approaches to KAPC not use the same missed approach procedure as the ILS/LOC approach?
While looking at the various instrument approaches for Napa Valley (KAPC), I noticed a discrepancy between the RNAV (GPS) Y/Z RWY36L missed approaches and the ILS/LOC RWY36L approach:

Why is it that the ILS approach is able to use a turning missed approach to keep pilot and plane clear of the high ground to the north, but the RNAV approaches to the same runway force you to either have visual contact with the high ground early, or outclimb it?  To me, it'd make more sense to have the RNAV procedures use a similar missed approach to the ILS, as then you could have an all-aircraft RNAV procedure with low minima, vs. one with high minima that works for everyone and one with low minima that requires a significant (more than twice the norm) missed approach climb rate.

As best I can understand from the TERPS, it's because there are certain criteria for RNAV missed approaches that wouldn't be met by copying the ILS missed approach.
Specifically, I found the following (see chapters 7 and 15):

In RNAV missed approaches "turns shall not exceed 120°", but the ILS missed approach requires about a 180° turn. There's some related information here about the FAA testing turns greater than 120° in RNAV instrument procedures, it looks like some avionics can't handle them properly.
RNAV missed approaches are made up of legs between waypoints, and the first leg after the MAP has a required minimum length "to allow the aircraft's stabilization on course immediately after the MAP". Unfortunately I couldn't identify what that length is, because the FAA's PDF quality is abysmal and some information is unreadable, but the ILS missed approach requires a turn after a climb of less than 300' (from 214' to 500'), so the distance traveled in that time would presumably be quite small. If the RNAV minimum leg length is significantly greater than that distance, then it might be necessary to continue straight ahead, as both RNAV approaches do.

I'm certainly not a TERPS expert and there may well be other reasons for not using the ILS missed approach, but those two points seem to show that the criteria for designing missed approaches is different enough between procedure types that you can't just 're-use' them freely.

I'd think that you could emulate the ILS missed in a RNAV procedure with two appropriately placed waypoints...but that doesn't deal with the leg length issue you pointed out, though!

@UnrecognizedFallingObject Yes, I think that's the point: RNAV routes are constructed out of straight legs that have a minimum length and can't be joined at more than 120°, which means a genuine curve isn't possible and joining together a series of legs might result in a 'circle' with a large radius. At least, that's my understanding of the TERPS.

This is definitely the right answer. The GPS is fix-to-fix, so the Missed Approach Fix has to be able to be sequenced as the next waypoint in the RNAV equipment, given the turning constraints.

GPS approaches and missed approach routing are designed point to point to point, so "climb to XXX then direct ABC" doesn't work -- there is no defined track to sequence to after the straight-ahead leg. So the GPS approaches can't use the same procudure as the ILS does.
There does seem to be a terrain or obstacle issue somewhere on the missed approach routing of the GPS approaches. So you can either fly the "Y" approach with a high MDA (so you start the missed approach higher, with less altitude needed to clear the obstacle), or you can fly the "Z" approach that takes you lower but requires a higher than standard missed approach climb gradient.
There is probably a reason that the approach designer didn't use a missed approach track that would look more like the ILS missed approach track (but done point to point to point), avoiding the obstacle even with a normal climb gradient, but we can't tell what that reason is. A minimum length of each segment and similar TERPS criteria would be my guess, but that is only a guess.

Look at where the missed approach points are on each approach. The ILS has you very low, and possibly unable to clear the terrain to the northeast, hence the turning procedure. The RNAV has you going missed almost 1000 feet above the ILS, so terrain clearance would not be as much of a factor. For either ATC or convenience reasons they probably prefer you to go missed to the north east, hence they have the RNAV go that way.

That's not true for the RNAV Z procedure -- the minima on that are much closer to ILS minima, yet it uses the same missed as the RNAV Y procedure, just with a minimum climb rate requirement.

The inclusion of a minimum climb gradient on the RNAV Y is due to the lower minimums for that approach. If it were an LPV only approach with only a 250ft DA, there is a good chance there would be a missed approach procedure similar to the ILS. However with the inclusion of the less restrictive (climb gradient-wise) MDA minimums, the use of a straight out missed is possible. The minimum climb gradient is no doubt based on the 250ft LPV DA, since including multiple MAP that are based on the minimums used for the approach are not desirable.

the NPAs could use the same missed approach procedure as the ILS currently does -- your argument is nonsensical (just consider for a moment what the missed approach procedure for the LOC approach to 36L is)

Could it be because you are using two different navigation systems?
Yes, you might be on the RNAV/GPS for the approach and have the ILS on a second display. But, why wouldn't you just use the lower DA on the ILS anyway?

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Operating a floatplane/seaplane on water through a drawspan?
Lets say that you were in a floatplane (whether it be Terry's floating Cub or a big ol' Martin Mars) and the only otherwise-reasonably-suitable landing spot in the waterway where you are trying to go, or the taxi route from your landing site to your destination dock for that matter, is crossed by a movable bridge (aka drawbridge) that will not clear your aircraft when the drawspan is closed.  How would you, the floatplane pilot, signal the bridgekeeper to open the bridge so you can land/taxi through the navigable channel provided, especially considering you don't have a foghorn to signal the keeper with, and the keeper only has a marine VHF radio, which you may not have?
Assume that the drawspan can clear your plane when open (always true for bascule and swing spans; landing under a liftspan would be rather challenging though), and that the bridge is operated by a local bridgetender 24/7 (lesser-used drawspans often require prior notice, and there are also remote-control drawbridges out there that use sensors and/or CCTV to indicate the presence of marine traffic to a bridge operator sitting far away).

Generally you wouldn't land in such a direction as to have your landing run take you under the bridge (and smaller bridges are often low-speed or no-wake areas). I lived briefly in Bayville, and someone in Mill Neck had a floatplane: They would usually land in Oyster Bay or the sound, then sail back into Mill Neck Creek under the Bayville bridge (which had to be opened at high tide for the tail to safely clear).

When I sail we use simple air horns to signal the local drawbridges. Something like this one is usually kept on the boat. I see no reason not to keep one in your float plane if you anticipate need to hail a draw bridge or just for general marine hailing. If memory serves, it's one long blast (4-6 seconds) followed by a quick one. Similarly you could opt to carry a hand held marine radio in your plane.
Now all of that is assuming you knew you were going to encounter a bridge. If you did not plan for it then you have a few options. If memory serves some (if not all) of the bridges have land lines and if you have a cell phone you may be able to call them (provided you can find the number). If you are flying a float plane you may (should?) have a PFD on board. Many PFDs have whistles attached. This, in theory should suffice to hail the bridge. The bridge attendant may see you floating there and open the bridge as well.
You can always try, um, yelling at the guy...
Now what if the bridge is broken, there is a long train stuck on it and the attendant stepped out for a cigar break and has no intention of returning for a while? You are in the end of the day in a float plane and you have a unique ability that most ships don't have, you can go over the bridge...

Your memory is correct: One long blast, followed by one short blast (within 3 seconds). The same response from the bridge tender indicates the bridge will be opened. 5 short blasts from the tender is a "No Open", at which point you'll wish you had that marine radio to find out if you should give up on getting through (the bridge is busted) or heave to for a short delay (e.g. the at the Reynolds Channel bridge the railroad has priority over marine traffic for some odd reason, and they won't open if there's a train coming - usually within 10 minutes).

@voretaq7 - that "odd reason" probably being that even a superheavy cargo ship like a container liner or oil barge can stop faster than a train. 10 minutes really isn't too long a time to bring an 80-car gravel convoy from a 50mph mainline cruise to a complete stop in anything less than an emergency. Then, once it's stopped, you have to get it going again. But, that was probably sarcasm :)

@KeithS It's odd in this case because this is a commuter railroad: even our "freight" trains are typically 15 cars or less (and none use that line). Also the Long Beach station the bridge serves is less than a mile from the bridge so trains are doing about 5MPH by the time they get to the bridge. (Counterintuitively the Broad Channel drawbridge that the NYC subway goes over is a marine priority bridge: Subway service to Far Rockaway is at the mercy of any sailor with a tall mast.)

Hmm. Probably something to do with a need to check and double-check that the rails are back in alignment after cycling the bridge, since there's a significant life safety impact (even at 5MPH). There may also be issues with the system that powers the trains along the bridge, where if the bridge is raised, the circuit along the rail between the two nearest stations is cut, so if anything's in that segment at the time the bridge can't be raised. Nothing that more tech can't fix, but we're talking about a fairly busy commuter connector so maintenance/upgrade time could be hard to find.

@voretaq7 -- I suspect the RR having priority has to do with train frequency vs. boat frequency -- commuter trains run fairly often compared to freights.

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How are pilots alerted to the publication of a NOTAM affecting their flight while in-flight?
With the length of flights in this day and age, it is possible for an activity to be published in a NOTAM, that NOTAM to be disseminated via the NOTAM system, and the activity to start taking place after a flight whose PIC should have received that NOTAM took off!  Take for instance a by-NOTAM restricted area activation with the minimum 4 hour advance notice, and a 777 whose crew flightplanned through the restricted area based on it being "cold" at the time they briefed their flight, which was oh, another 4 hours before the NOTAM for activating said restricted area was put out.  Keep in mind that the 777 crew took off 2 hours before the restricted area was activated...
How is the flight crew of our hypothetical 777 supposed to find out that the restricted area they were told was cold during their preflight briefing is now hot?  (Of course, this applies to other kinds of NOTAMs as well, some of which can pop up with even less notice; for instance, a mishap-induced runway closure could occur at any time, and a long-haul flight crew would probably rather get that memo before they seek a landing clearance!)
Also, assume this is in US airspace.

The case of a restricted area is covered in: Restricted Area “popping up” around you — can it happen, and what do you do about it?

In the case of the 777 (or any flight operating on an IFR flight plan) it is ATC's (and the pilot's) responsibility to vector the flight around restricted airspace. In the event of pop-up NOTAM's, ATC will do their best to inform you, especially on an IFR flight plan. The key is you should be talking to somebody, or at least listening in. I have a feeling though that you want a little more...
Flight Information Services (FIS-B) provides weather, text, graphical weather, NOTAMs, ATIS and other information to aircraft in flight over the UAT link. ADS-B (ADS-B Out mandated for all aircraft in controlled airspace by 2020 in the US) will be able to provide similar data to aircraft in flight all the way down to small GA (if they have ADS-B In capabilities, or ADS-B receivers like Stratus).
So the crew of your hypothetical 777 will be notified multiple ways:

ATC will notify them about the need to vector around restricted airspace.
ATC will notify them about the closure of an entire destination airport as filed
NOTAMs will pop up on the FIS-B display in the cockpit
The ATIS or automated information broadcast will be updated to include NOTAM'd airport or runways
Crew will see the FIS-B display when they check destination airport weather/closures enroute
At the very least, ATC will notify the flight on approach ("Airport is currently closed, please continue to the filed alternate" or something like that)

Now, on the flip side let's say that you are a J-3 Cub with no radio humming around to your local uncontrolled field. The field was just closed due to a water buffalo migration and NOTAM'd out of service until the beasts can be removed from the property. You are on a 5 mile final and all the water buffalo are hiding in the woods next to the runway...
If you land you've violated the NOTAM and airport closure. This may warrant a call to your FSDO but you will probably be able to explain that the NOTAM wasn't active or identified prior to departure and they'll let you off (and the next thing you should do is go buy a handheld radio). At the very least you should make a report in the Aviation Safety Reporting System (ASRS) in case somebody raises concerns.
Either way if possible the FAA recommends a 4 hour minimum notification time for closures that can be planned. Why 4 hours? Most GA aircraft have about a 4 hour endurance and most domestic flights are less than 4 hours long. Obviously not everything can be planned, but ATC will work with aircraft in flight to disseminate the information as required.

Small correction: ADS-B In is not part of the 2020 requirement, just ADS-B out

Another small correction: It isn't only ATC's responsibility to keep airplanes out of restricted airspace, it's a joint responsibility between ATC and the pilot (hence the question being very valid).  See Can you bust a TFR while operating under IFR?.

@TomMcW Thanks, I clarified.

@Lnafziger Thanks, again, clarified.

If you call for a briefing, you're out of luck, but if you get a briefing online using Leidos Flight Services (formerly Lockheed Martin), you can easily solve this problem by registering for briefing updates.

Once you've done so, you can choose which elements will trigger an email or text message notification sent to you as soon as any elements of your briefing change.

I use this feature constantly - it's terrific.

The body of the question asks about NOTAMs that come out between a briefing and takeoff, but the question title asks about NOTAMs that come out in flight. This answer covers the former.

My intent was to ask about NOTAMs that come out in flight -- I clarified the example scenario in the question.

This answer could be an answer to either question, depending on internet access in flight.

Unless the aircraft were on a VFR flight and not in contact with ATC during any part of that flight, ATC would notify them and vector them around the obstacle.
That's why they're there after all... If he were VFR and out of contact with the world, even unicom/guard, the only way to contact him would be through another aircraft pulling up alongside and forcing him to change course. But flying VFR without contacting ATC into controlled airspace is a big nono as is, so he'd be in trouble regardless of whether there was an airspace restriction on top of the existing airspace rules in place at the time.
Think Mathias Rust and his silly flight to Moscow for a prime example of the latter scenario. The Soviet air force tried and failed to intercept him (the reason for that failure is political, and irrelevant here), but on landing he was arrested and his aircraft impounded. Expect something similar to happen to your idiot pilot who flies e.g. into New York restricted airspace, whether there is a further restriction in place that day or not.

There is on one way to get the latest on the spot NOTAMS the instant they are published.  If an aircraft has WiFi and the flight crew periodically obtains NOTAMS throughout the flight is one way.  Critical and pertinent NOTAMS may also be passed along to controllers who will disseminate them to pilots operating in airspace affected by a NOTAM.
Due to the capricious nature of VIP TFRs or other critical NOTAMS, the FAA is generally forgiving if a pilots has conducted a competent preflight and researched applicable NOTAMS to his/her flight prior to departure.  I talked with an F-22 pilot a couple of years back who had some experience chasing errant bugsmashers out of TFRs.  His advice for legal CYA: ALWAYS call flight service an drew request a standard flight briefing, including a NOTAM briefing prior to flight.  You now have a permanent record that there was no knowledge of a NOTAM affecting your planned flight and that can be used as evidence in court.
As for the 777 example you listed above, it is almost certainly going to be operated under IFR rules and will be under the control of ATC who can grant you clearance to enter a restricted area; it's their hinder that's in a sling if it goes SNAFU, and not yours.

"If an aircraft has WiFi", no... if the aircraft has Internet connection rather.

mins.......really?

WiFi is for the local area network, like wired Ethernet. The connection of the LAN to an Internet access point is not done using WiFi, but generally satellite communication gateway (technically to a POP for Internet point of presence). See this.

WiFi, Ethernet, Token Ring, I2C, satellite, RFC 1149, UMTS, ATM, etc, are implementation details. They are all means by which to establish some level of network connectivity among different computers. They can be used to connect to the Internet, to a different IP-based network, or some non-IP-based network.

@MichaelKjörling: The actual name of the protocol described in RFC 1149 is IPoAC. However IPoAC is not compatible with aircraft, it is known to interfere with engines.

@mins Yeah, RFC 1149 was a bit tongue in cheek. I figured I'd throw it in and see if anyone noticed. (That said, I have little doubt that the exact same infrastructure could be used as a transport layer for other protocols as well.)


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How is the direction chosen when landing a seaplane on water?
When using a runway, many factors are taken into account to choose the landing direction.
A lake can be used in almost any direction by seaplanes. I imagine wind is prevalent, but I guess other elements such as waves, form of the body of water surface, water flow should also be taken into account.
What are the elements taken into account when choosing the direction to land a seaplane onto a body of water, and how do thoses elements influence the direction?

If you're on a river, it's generally considered good practice to operate with the current rather than against the current unless conditions dictate otherwise. On a river there tend to be lots of obstacles: power lines, bridges, river bends, rapids, boaters, etc. Another major factor is where on the river bank that you're leaving from or where you're wanting to dock or beach.

Here is a nice little article on it. But in general the small waves on the water will curl with the wind and can even be used as a wind indicator. For calm water you can obviously chose your direction based largely on wind (but if the water is very calm there is likely little wind). Obstructions will play into choosing direction as well and it is advised to overfly the intended landing area before touching down. As for rough water landings the article states

It is impractical to describe an ideal rough water procedure because of the varying conditions of the surface. In most instances, though, the approach is made the same as for any other water landing. It may be better however, to level off just above the water surface and increase the power sufficiently to maintain a rather flat attitude until conditions appear more acceptable

Your elements are (in no particular order)

Obstacles
Wind
Landing Area (you need enough distance to actually land same as a paved strip)
Possible Rough Conditions

You must also keep in mind where you can actually land a seaplane. Not every body of water is legal to land a sea plane in (emergencies aside). You may want to check out this recently released book on arguable the first guy that flew a seaplane around the world.

Your last bit would be a good addition on this question.

In addition to that article you might want to check out the FAA's "Seaplane Handbook" - Chapters 4 (Takeoffs) and 6 (Landings) would be particularly relevant.


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How are temperature differences handled in a jet engine?
Given the graph in this answer, the temperature are quite high inside a jet-engine, even greater that many metal's melting point. I understand high core temperature are efficient.  A jet engine is designed to work for several hours at those high temperature.
Moreover, starting the engine (i.e. going from ambient temperature everywhere inside the engine to more than 1500°C in the combustion chamber while not significantly changing the temperature at the first low pressure compression stage) may be quite stressful for material.
My question is in two parts:

How is the high temperature handled, especially in the combustion chamber and the high pressure turbine? I read somewhere that the turbine can be cooled by air flowing inside the blades but I cannot find the reference. I also wonder where this cooling air comes from.
How is the stress on material due to temperature changes (between full thrust and shut down, and maybe when changing thrust in mid-flight) handled?

I hope that the answer covers all the points. Unfortunately I do not think that going in greater detail would be feasible, as we are covering the arguments of 2-3 chapters of a good gas turbine book.

@Federico you may still put some links to thoses chapters for further readings

My main textbook was "Gas Turbine Theory" from Saravanamuttoo, Rogers, Cohens and Straznicky. I do not think it can be legally found for free on the internet, and I have no direct links.

Something I haven't seen mentioned yet - often the turbine blades themselves have air channels inside, and sometimes additional film cooling on their surfaces.  See for example http://aviation.stackexchange.com/questions/14454/why-are-aircraft-turbine-blades-made-of-nickel-alloys and https://en.wikipedia.org/wiki/Turbine_blade#Methods_of_cooling

@Andy it is mentioned in the question itself: I read somewhere that the turbine can be cooled by air flowing inside the blades and in my answer (point 2)

1. The combustion chamber
Temperature here is usually controlled via design of the chamber shape, in particular of the location where combustion occurs vs the airflow.

Image source
In the image above you can see that the fuel line (2) terminates in a nozzle. The nozzle will turn the fuel into tiny droplets to increase the surface area and hasten the combustion process.
Indicated with (6) are instead the main air holes: the cool air coming from the compressor (on the left side) enters the chamber with high pressure from these holes. Note that the holes are distributed in an annular pattern: high pressure air will be entering from all sides of the chamber.

The result is that the flame will not directly touch the walls of the
chamber, we then got rid of conductive heat transmission.
Convective is a non-issue: cool air keeps coming and hot air goes
into the turbine.
Radiative heat transmission might be an issue, but the new air
incoming will cool the walls via conduction.

The engine can thus run without the combustion chamber melting. Note that the use of specific materials does greatly improve the conditions, as higher temperatures can be tolerated, and thus better efficiencies achieved.

2. The turbine cooling air
The air is usually bled from a stage of the compressor, usually a high pressure stage, in a similar manner as done for the air used for the passenger compartment.

3. Thermal stresses
a. Short term
Over the duration of a flight the blades will warm up when the engine is turned on and cool down at the end of the flight. Intermediate load variation do not have a significant impact.
Even the initial warming and the final cooling do not pose a significant problem. The only effect to be taken into account is that the rotating hot blades will become slightly longer: a special material is placed on the opposing stationary side so that the gap is minimal during operation and the losses due to the air going around the blades (instead of between them) are reduced.
b. Prolonged
The most problematic aspect here is the so called "creep": the blades, after prolonged use, will tend to change shape, because they tend to be more malleable at high temperatures, exactly when they are under high tensile load. This becomes a problem over the lifetime of an engine, not during a single flight.
To mitigate this problem the blades are nowadays manufactured as single crystals: each blade is a single solid block of metal and not made up af many tiny crystals as the metal tools we use everyday. This is because under tensile load each of the crystals can slide over its neighbors (and high temperatures facilitate this) changing the shape of the blade. To visualize it, think of a rubber band that does not go back to its original form.
Having a single crystal prevents this sliding, giving more strength to the blade.

What is the typical compressor exit (combustion chamber intake) temperature? I mean maximum temperature just before combustion.

@Kozuch that will depend heavily on the engine. I don't have a number ready to give.

I will actually be happy for any values for any engine. Do you know where to find some? My search is failing so far.

@Kozuch no. but you can try asking in chat.

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When taking passengers, what should I do to prepare them?
What kinds of stuff should I think about in terms of taking other passengers flying in a small airplane?  Many potential passengers have never been in a small airplane.

A very good pre-flight briefing, including the use of the radio in an emergency. It also depends on what kind of flying you are doing, just a scenic joy ride or cross-country? It may be important to ask if they get carsick, and stay near the home airport until you see how they respond to turbulence and flying in general so you can get back on the ground if needed. I always swipe a couple sick bags from commercial flights to have with me just in case, nothing worse than a passenger throwing up on the interior while trying to land.

I get the feeling that this is a duplicate of some question on the site, but can't seem to find it...

This is similar, but not an exact dupe; it's about passengers who want to fly the plane.

I had a feeling too but I searched first.  Twice.

I go through the SAFETY checklist with all my passengers.  The FAA recommends this as well.

Seat Belts - This is where they are and how to use them.
Air Vents - Here are the air vents and how to use them
Fire - In case of a fire here is the location of the fire extinguisher and this is how you use it. PASS method.
Exits, Emergencies and Equipment - Here are the exits on the airplane and here is how to open the door.  Know that you are in good hands and that I have been well trained to land safely under most situations.  If for some reason an emergency occurs in flight follow my directions.  If we need to land off the airport, I will ask you to pop open the door just before landing to ensure we can exit the airplane safely.  Here is any safety equipment that you may want to use on this flight. i.e. supplemental oxygen.
Traffic and talking - Please point out an traffic that you see and I will do the same.  Please no talking while I am on the radio.  Once we start taxiing to the runway please remain quiet til we are far enough away from the airport.  I will let you know when it is safe to talk again.  When we come in to land, I will ask that you remain quiet, unless an emergency situation occurs, till after the landing is complete and we are taxiing back to parking.
Your questions - Do you have any questions?  Alright, lets go have some fun!

Thank you.  This is the kind of checklist I was looking for.  One thing popped into my mind as I was reading the answers here.  Traffic.  Often, people don't think that what they see can be useful.  Passengers often assume that the pilot is some kind of genius which we're not.  Telling a passenger about the traffic clock (traffic at 9 o'clock) could do wonders and make you laugh in the cockpit.  Happy flying.

We were required to give what amounted to an "airline" briefing before each flight.  We were also required to have those stupid little briefing cards for each passenger (of which at least one was stolen on each flight).  Our Cessna 210, oddly enough, seemed to have the most popular cards!  We couldn't make enough of them.  Maybe people just think it's silly that a "little Cessna Piper Cub" has a briefing card just like a "real" plane.
I quit flying professionally in 2013 but continue to use 135.117 as my standard briefing.
•these are the seatbelts, this is how they work.
•these are the exits, this is how they work.
•these are oxygen masks, this is how they work.
•your seats recline but please leave your seatbacks in the upright position for takeoff and landing.
•the fire extinguisher is here, this is how it works.
•please don't smoke.
•there is a survival kit in the back of the plane...or in my flight bag...or both
•(front seat passenger) these are the controls, please keep from touching them.
•if you see another plane, let me know if the wings are on the top or the bottom and the number of engines you see (prevents passengers from reporting every single glint that may possibly be an airplane)
•if you have any questions, PLEASE ASK!   If I things are busy and can't answer you immediately, I'll ignore you but circle back later.


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What's the best way to get started flying?
I'm considering flying.  I'd like to find out what is the best way to start.

Find a flight school and take a discovery flight. What country are you asking about?

Consider gliding. It's much much cheaper...

I'm in Israel.  I don't know anyone who flies here so I guess I'll follow the advice above.

Your profile says New York. Consider getting flight training in the US; it will be much cheaper. Or in Europe.

Thanks.  I'll consider that.  I heard GA in the US is the best in the world.

I find climbing into the aircraft a good first step ;) Sorry, couldn't resist!

The best way to start is to find and visit a local airfield near where you live.
Most local airfields have some level of training taking place, and if the closest to you does not then another, perhaps slightly farther afield, will do.
Visit one of these flying schools and ask to speak to an instructor, a CFI, or an examiner. They will give you more details such as the aircraft they fly, the typical syllabus and the expected costs.
From there, you might like to start with a "trial flight" - typically 30-45 minute flight where you get to take controls and get a feel for piloting an aircraft.
Good luck.

Thanks for answering.  It's really more of a dream of mine but I'll try to follow your advice.

@user6035379 it starts as a dream for everyone. Its up to you if you want to turn it into a reality!


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Can military officers change occupation to become pilots?
From what I have read, the paths to become a fixed-wing pilot in the Air Force, Navy, and Marines, are to go to a military academy, enroll in ROTC in college, or go to an officer training school after earning a bachelors degree. In any case, a person will know if they are going to become a pilot before they become a part of the military.
For someone who is willing to become an officer in the military but is not offered a pilot slot when they join, is it possible for them to change their occupation before their contract has ended?

Voting to close because this is a question best addressed to a recruiter (and then triple-checking their answer).

It's still about Aviation, even so. And, "xyz can better answer that question than we can" isn't listed as a reason to close an otherwise on-topic question.

@RalphJ +1 We shouldn't be too trigger happy to close questions!

But isn’t this about military career path rather than aviation per se.

In the USAF, it has, historically, been common for rated Navigators to be selected for pilot training, and possible, though less common, for young officers in other career tracks as well.
That said, this process is

competitive (so certainly not guaranteed for a particular individual), and
dependent on the "needs of the service", so what is going on "now" may be entirely different from what was going on "then".

Also, the demand for UAV operators may have changed this dynamic considerably; it may be a far different process to become a "drone pilot" from a non-rated field, than to become a "real pilot."  Talking with active duty officers (not recruiters) who are up to date on this landscape is indispensable for getting the most current picture.

Navy and Air Force in the US regularly see migration between officer specialties.
A friend who had a non-pilot Navy job, now flies patrol missions.
A co-worker who had a logistics job (math major in college) with the Air Force, later put in for pilot training, and was accepted.  He eventually was assigned to Beale and flew U-2s and became an instructor pilot in the same aircraft.
Similarly, there are many pilots trained, who eventually take "desk jobs".
It has been told many times, that the best time to maneuver to a pilot job is prior to extending one's contract. Changing mid-contract may be problematic.
There are numerous limitations, age, physical, and there are also qualifying examinations involved.
I do not know the current regulations, but one might check out the reserves for opportunities.  I know one right seater in 747s who is now flying A-10s on his days off.  He has been deployed three times.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Can “old people” entering the aviation industry make money as a pilot?
I become a private pilot just over 2 years ago. I’m 52. I always feel better about the world and my place in it when I’m flying. I currently make a very comfortable salary as a software engineer.
A slightly younger acquaintance who is a burnt out dentist is pursuing his private with aspirations of switching careers eventually. Though he couldn’t tell me to exactly what. I must admit, I find his idealism inspiring, but am skeptical.
My limited awareness of earning money in the aviation industry is a) older people working as CFIs who basically “break even” but at least don’t go broke doing their hobby or b) young people who spend huge sums of money to go to flight school, and then be beholden to an airline, flying busloads of people around for many years to pay it all back.
Are there realistic “last 15 years of work” paths for people such as myself or my dentist friend? Neither of us expects to make as much, but selling everything and working for single adult entry wages so we could fly isn’t realistic either.
Or is the only realistic path that of my aged instructor (don’t quit your day job; find a way to subsidize your hobby)?

Does it need to involve flying, or would a software engineering role in the aviation industry count?

Im specifically interested in the notion of “flying for a living” here.

Regional pay is a lot better than it was, but it’s going to be a grind getting there.  I think this is a mostly opinion based personal decision, and maybe not the best fit for this site, but a great discussion over coffee because I’ve tread some of this ground…

An issue you may come up against is that "market wages" for low time pilots are what they are, and are driven by the large supply of pilots who are entirely willing to be "working for single adult entry wages so {they} could fly" since that's where they are in life.
To stand out in that market, you'll need to find where your age works for you, and having the age but without the experience, that may be hard.  If I were to get back into General Aviation again, I'd probably prefer learning from a CFI who understands where the gaps are in my knowledge... decades of flying big airplanes translates less well into some areas than into others, and I'd need instruction tailored to those areas where my experience doesn't match up well with flying small airplanes.  And that means that the 65 or 70 year old former airline pilot might be more preferable for me than a CFI who's far closer to my kids' ages than to my own.  But that has as much to do with his experience having done what I've done and taught people who've made a similar transition, as it does with just chronological age.
Some older students will prefer a CFI in his 50's over one in her 20's; is that enough that you can exceed entry-level CFI pay consistently? Not entirely sure about that.
There are places you may be able to fly for cheap or free on the weekends, flying regularly if not vocationally.  A friend who started flying in his 40's became a regular tow-plane pilot at a glider operation.  The pay wasn't much (or maybe anything, if it was a club), and the hours may not have been enough for the pilot looking to build time & get to the airlines quickly, but neither of those was what he needed.  Opportunities like that, flying jump planes for skydiving, or other similar things tend to be one-off situations that you'll find individually; they're much less mass-produced than flight schools with many CFI's flowing through their pipelines... but the fact that you don't intend to move on as soon as you get picked up by a regional may work in your favor at these sorts of operations.


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What airframe design is best for stormy weather?
Consider picking a plane for weather study. This plane will intentionally fly into weather systems (e.g. inside the eye of a hurricane) to collect scientific data. It will be equipped with on-board weather radar and other atmospheric sensors.
Which airframe designs are most suitable for this type of flying?

4 engines is probably a must for reliability
Piston? Turbo-prop? Turbo-fan?
Low wing? High wing?
Low / high aspect ratio?
Delta wing? Sweep wing?
Conventional tail? T tail?

You get the idea...
EDIT: I would also like to know why the current planes are chosen. For example, if delta wing is not used, then it suggests a certain criteria which cannot be met by the delta wing design (e.g. requires high AoA at low speeds).

NOAA uses WP-3D Orion to collect data within the hurraine.

NASA has an "Experimenter's Guide" in pdf form with all kinds of specs and considerations for the P-3 Orion.

In observing the configuration of the current aircraft used for weather study, it's important to also note that those planes were originally built for different missions that allowed modifications for such a special purpose.
The P-3 was built as a maritime patrol plane, which is a role not all that different from weather observation. It requires good range and endurance to allow the plane to fly out to sea and remain there long enough to accomplish its mission. The primary mission is using sensors, either onboard or deployed from the aircraft. The plane must also be able to withstand more time spent at lower altitudes and in more turbulence than typical aircraft.
The C-130 was built as a transport plane. This requires good range and payload capacity, both in weight and volume. These attributes have allowed it to serve in many roles, such as attack, special operations transport, and electronic warfare. As both aircraft were originally built for the military, they are built to withstand higher loading than typical civilian aircraft, which is useful when flying to bad weather.

4 engines are less efficient but provide redundancy - Both aircraft have 4 engines, as this is a good compromise between size of engine and propeller for this size of aircraft, at the time at which they were designed (around 1960). This primarily provides redundancy. The plane is required to be able to fly with one engine failed, and controllable with two on the same wing failed.
Turboprops are efficient at moderate speed - Both aircraft are also powered by turboprops. The primary roles for the aircraft do not require high speeds or altitudes, which is where turbofans have an advantage. Turboprops provide good power and efficiency at moderate speeds and altitudes, which is acceptable for shorter cargo missions and maritime patrols as well as weather observation. It's worth noting that the US Navy is replacing the P-3 with the P-8, which is a twin engine jet aircraft. A large part of this is likely due to the availability of an existing aircraft design, not being worth the cost of designing an entirely new plane. Although two engines provide less redundancy, they can still provide a similar level of reliability. Japan designed an entirely new maritime patrol plane, and opted for 4 turbofans. Although turbofans may require more fuel, they do allow higher speeds which allows the aircraft to reach its station faster.
Low wing may be a more versatile configuration - The high wing of the C-130 is mainly to allow easy loading and unloading of cargo by keeping the fuselage closer to the ground. This is less important for a weather observation role, though it does allow better downward visibility from the cabin. The P-3 sits higher above the ground, which allowed for a radar to be mounted underneath. Mounting sensors on top is certainly an option but may require modifications to retain stability. One might conclude that a low wing offers more versatility in this regard.
Moderate aspect ratio with sweep to match speed - The wing design will depend on the speeds for which the aircraft is designed. Low aspect ratios and high sweep or delta wings are good for reducing drag at higher speeds. There is no need for very high speeds in a weather observation aircraft, so these would seem to be poor choices. High aspect ratio and low sweep are good for reducing drag at lower speeds, which can maximize endurance. Though endurance is important for weather observation, these designs also have higher wing bending and generally lower top speeds. Both the C-130 and P-8 have moderate aspect ratios and low sweep, which offers a good compromise for strength and efficiency. Jet aircraft fly faster and generally use moderate sweep and aspect ratio.
Conventional tails can be more robust - T-tails have some issues with control and stability, and this prevents them from being used in most cases. The T-tail is mainly useful when the normal position of the horizontal stabilizer is taken up by engines or cargo doors, or would place it too close to wash the engines, or if efficiency is a high priority. Control and stability are particularly important when flying in adverse weather conditions, so if there is no other reason for having a T-tail, a conventional tail works better. All of the aircraft mentioned above have conventional tails.

The 4 engines was a good feature for the NOAA researchers studying hurricane Hugo in 1989. The no. 3 propellor failed catastrophically and pieces of it partially damaged the no. 4 prop, although no. 4 was still able to keep operating. The P-3 is actually designed to shut down one or both outboard engines to maximize loiter time.

To answer this, let's look at the planes primarily being used for this task today:
the  Lockheed WP-3D Orion

and the Lockheed WC-130

These planes both feature 4 engines like you suggested, likely both for reliability and for the fact that they are rather large planes in order to maximize instrument and sensor space, as well as stability.
They are both powered by turboprops, which is likely due to the compromise provided between speed, range, efficiency, and reliability.
One has a low wing and the other a high wing, indicating that this is not a primary concern, as they have both been operational for decades.
The aspect ratios are relatively moderate, again indicating a compromise between performance and stability. The wings feature little sweep, reflective of the emphasis on stability and range over speed.
Finally, both feature a conventional tail, suggesting that simpler, more reliable designs are favored over designs that are more complex to maintain.

I think that the logic of this answer is somewhat flawed. Both the Orion and Hercules are planes that were not specifically designed for weather observation and, as such, any commonalities of their features might just be coincidence. They show that, for example, a four-engined turboprop is at least "good enough" for weather observation but, hey, maybe a three-engined turbofan would be ideal and it's just that no such planes were available for conversion at the time and it was too expensive to design a new plane from scratch.

Planes that actually fly into a hurricane for such purposes all the time are the C-130 and P-3 both of which are quadruple turbo-prop airplanes. As the C-130 is high-wing and the P-3 is low-wing, that part does not really matter. Both planes also have relatively straight wings and not swept back in any way as well as conventional tails. The P-3 has an aspect ratio of 7:5 and the C-130 has an aspect ratio of 10.1.
So basically, get a military plane with 4 turbo-prop planes and you are safe to go as we do it nowadays.

Is that because the aerodynamics requirement for flying into hurricane is very similar to military transport plane? I'd like to know more about what's special about those planes that are chosen, as opposed to say, a Boeing 747 or a B52.

@kevin I'd say cost, most likely. The organizations that do this work are both either military or government related, so it's probably a lot cheaper for them to reuse old transports rather than buy new planes. In addition, these transports were designed mainly with ruggedness and survivability in mind, and can take a worse beating than a 747 or 757 that is designed for speed and efficiency.


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How is tire rubber removed from the runway?
Every time an aircraft touches down, the tires are spun up rapidly. As a result, some rubber is left at the touchdown zone.

(image source)
As time goes on, more rubber is accumulated at the touchdown zone. How is this rubber removed from the runway surface?

Isn’t more rubber better as it would provide better grip?


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Are remarks in the Chart Supplement (A/FD) "regulatory" or "advisory"?
StallSpin's answer on the recent question about VFR traffic patterns has got me thinking about the "Remarks" section of the Chart Supplement (formerly the Airport/Facility Directory).
We are all taught in training to review the Supplement entry for airports we intend to visit (part of FAR 91.103's "become familiar with all available information" requirement), and to comply with any restrictions noted - typically things like "no touch-and-go landings", "Standard traffic pattern required of all aircraft", "Prior Permission Required for jet aircraft", etc.
Aside from it being The Right Thing To Do, and avoiding the possibility of local fines/sanctions, are the remarks in the Supplement "regulatory" such as to require compliance, or are they advisory where compliance is encouraged but not mandatory?

A required rule in the airport/facility directory is required. It is a very good idea to check the AFD entry online (or on paper) before you fly to a new airport. It just takes a second and you can learn important things, such as "NO DEPS AFT 2230" or "PPR FOR TKOF ON RY 15. CTC FBO 970-920-2016" (Aspen).

Yes, but how does one tell the difference between a "required rule" and a "request" - some are obvious (Pilots are REQUESTED to avoid overflight of housing development... versus Prior permission REQUIRED for takeoff on runway 15), others are not. (I generally just assume everything is required unless it's glaringly obvious that it's not, but something I could point at which confirms that would be nice...)

By the wording. If it says "recommended," "requested," or "should," it's optional. A definite statement such as "No departures after 2230" or anything with "PPR" is a requirement. "STANDARD TFC PATTERN REQUIRED OF ALL ACFT" is a requirement. However, it's a little ambiguous in that it does not say where to enter the pattern.

That's basically been my conclusion as well - I've never been able to find anything either in the FARs or the AIM saying "Do what you're told in the AFD", but I've always chalked it up as "regulatory" based on a conservative interpretation of 91.103.


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Why haven't we seen virtual reality jet piloting system yet?

Swedish technology aims to allow truck drivers to work from home.

Why haven't we seen virtual reality jet piloting system yet?
What are the barriers to the introduction of such technology?

What do you mean by "virtual realtity jet piloting system"? There are many UAVs, including turbine powered,  that can be operated remotely. Does that not qualify?

Please explain what precisely you mean with virtual reality, and how the linked video is related to your question!

@bogl VR is something which is itself fake but gives an experience of reality.

@bogl in the link, we see that, the driver is sitting in a simulator-like environment. if this same technology is used by military-jets, the lives of pilots could be saved.

Watch the video again, it is not a simulator. It uses 2D cameras and displays. No VR is involved.

@bogl, I don't say it's a simulator. I said, it's simulator-like. It covers 180 degrees.

The screen is large and curved, but it  has very little to do with VR. Is your question about VR, or what else?

Doesn't F-35 have it already?

No it doesn't @user366312, the pilot is in the cockpit.

Related

Here's a similar, but not completely the same, question: Can commercial airplanes be converted to drones?.  Maybe you'll find answers to your question there

Virtual reality, (fake reality) and remote operating (reality) are two very different things...

This technology is well known in aviation, and it is already in use for unmanned aerial vehicles, mainly for military use.
Obstacles that prevent remote control of passenger carrying airliners at present include:

Fail-safe behaviour (What happens if the remote link is interrupted?)
Cost calculation (The introduction of such a system would be very costly)
Acceptance of passengers (It is a re-assuring feeling, when the pilot puts his/her own life in the 'same boat')

Further to that, remote control competes with automation. Subject to opinion, automation has the potential to perform better in all the bullets that I listed.
Note that similar research is ongoing for cargo ships. We will probably see automated and remote controlled sea going vessels much sooner than airliners.

This technology is well known in aviation, and it is already in use for unmanned aerial vehicles, mainly for military use. --- not true. UAVs don't use virtual reality. They only use 2D cameras and videos.

Same as the trucks in the video you have linked. 0:15 "remote controlled trucks. 2:25 "remote drivers". There is no mentioning of virtual reality in that video, or can you point me to it? If your question is about VR, you better delete the link, and explain how you envision VR to be used. At present, it is not clear from your question.

"It is a re-assuring feeling, when the pilot puts his/her own life in the 'same boat')" - It's more than a feeling, I think.  The pilots are the only people on the plane who have the safety triangle: The knowledge to judge safety, the authority to not fly or alter the flight plan, and a deep personal stake in the outcome.  Remote piloting would break the triangle and safety will suffer.

This is technologically possible, a commercial jet could be flown remotely like a drone is, through automation and satellite communications. As you allude to there are barriers.
Dealing with problems remotely is harder, recognizing and dealing with problems is challenging when you are removed from the source of the information. When you are in the cockpit you have more information at hand. We would have to accept some losses as a result of bad data. (Note that there are some advantages to automation, but that's not the question)
One major barrier is the lack of satellite bandwidth. To be effective a great deal of information must be transferred between the airplane and the pilot(s), like telemetry, commands, and high quality panoramic video so pilots can see and avoid other traffic. That is a lot of bandwidth! If all airplanes were flown remotely we would need many more satellites to handle it all, which would be expensive.
There's a big risk in relying on satellite communications for flying passenger airplanes. Satellite communications could be disrupted by jamming or solar activity, imagine having a thousand airliners in flight and losing comms with them all! There would be no way to completely mitigate against this risk.
Another major barrier is the passenger perception. Most passengers would not want to be in an airplane flown by a person in an armchair half a world away, they'd prefer someone with some skin in the game.

Significant increase in the attack surface for unauthorized control as well.

For sure @BowlOfRed, although as an information security consultant I wouldn't say it's a barrier, only a surmountable challenge which would need very solid coding. More of a concern would be jamming, or a solar event damaging satellite communications while airplanes are in flight. I may add that in...

Bearing in mind that a pilot sitting in the plane is trained to handle a loss of comms (as most here know), while a pilot sitting in an desk chair at corporate HQ can do absolutely nothing for the plane over the South Pacific that he just lost communications with.

Sounds ideal @FreeMan, if you want to become a character in Lost.

Or a character in Dead. ;) (Haven't seen Lost, but I get the general idea. I have no idea if Dead is a show or not...)

The first season of lost was good, liked the characters. In the second season it was like 'now that we have you we are going to draw it out for many years', they started cycling characters through it, introducing them just to kill them off and I lost interest. The premise was they were all air crash survivors (or were they?)


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Why do MP and RPM adjustments have to be made in a specific order in constant-speed props?
Can anybody explain why do I have to pull back RPM lever first and then pull back MP after climbout when setting up my cruising speed MP/RPM combination. When I make an approach to land I do vice versa - firstly adjust MP (pull back to around 15) and then RPM (set to full).
My training aircraft is Diamond DV20 with automatic mixture control. It has only Throttle and RPM levers.

When setting cruise power, if you were to set the manifold pressure first, it would not remain constant as the RPM is reduced. It would have to be re-adjusted after lowering the RPM.
When adjusting the RPM lever you are actually controlling a governor which maintains a constant RPM. Any change in manifold pressure will not cause a change in RPM.
So adjusting RPM first just makes it a little simpler to set your power.


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Is having a history of seeing a therapist not allowed for pilots?
In a recent question someone said:

I thought about seeing a therapist, but as I want to work at a major company, I don't know if you're allowed to have a history of seeing one.

Is it true that having seen a therapist a bad thing? If yes, why? It doesn't make sense to me.

Please specify your jurisdiction

For a military pilot, yes, this can be an issue. For a commercial one, probably not, depending on the type of disorder you are having treated. Germanwings 9525 added significant more hurdles for those with mental health issues from being in the cockpit. Lubitz had suicidal tendencies prior to becoming a pilot.

@J.Hougaard I don't have a particular jurisdiction in mind, I was asking out of curiosity from the linked question. If the jurisdiction in relevant, please feel free to write a more open answer or specify whatever jurisdiction you consider relevant :)

@RonBeyer Looks like an answer ... or the start of one.

@RonBeyer But in that case, the root of the problem is the disorder, not the very fact of going to a therapist, right? People go to therapists for all sorts of reasons. Also, if someone hides their disorder and doesn't go to a therapist, that is even worse than having a pilot who treats himself...

From a military standpoint, self-treatment is better than getting help because one disqualifies you and the other does not. In the US at least, any history of depression or mental disorder is automatically disqualifying for military pilot service and even other service like Officer Candidate School. For GW9525 the act of going didn't disqualify him, it was that he went and his doctor disqualified him and he hid it. Because of that companies may now take a more proactive approach and assume. This is jurisdiction dependent because some have laws about discrimination for mental health issues.

@RonBeyer -- The above comment ought to be made an answer.

This can be difficult to answer, but I'll try from a US/FAA perspective.
Military Service
If you want to become a military pilot you cannot have any history of mental or psychological disorder This is from the perspective of starting out to become a military pilot. If you are already a military pilot and have some kind of mental/psychological issue that you need addressed, there is a process for doing that and returning to service. From this standpoint, self-help and "keeping it to yourself" is better than seeking treatment since you will be disqualified outright.
Personal Anecdote
How do I know this? This is exactly what happened to me. I had seen a psychologist when I was 8 or 9 years old (because he was a quack and convinced my mother (who was being treated for depression) that I needed help too). This made it into my permanent medical record. I applied for military service with the US Marines during college with the goal of becoming a pilot. I took the Air-Force Officers Qualifying Test (AFOQT) and passed with a 98% (the highest my recruiter had ever encountered). When it came time for my MEPS review they found the history (I disclosed it at the beginning, they found it via my disclosure and I provided additional documentation when asked) and disqualified me. I appealed to the review board and was denied. I appealed again, denied, and you only get two appeals (and the only recourse after that would be a Congressional/Presidental appointment). They told me I was eligible to enlist, but not eligible to be an officer.
FAA Medical Perspective
The FAA takes a different stance in that you are required to disclose to the AME any mental health visits during the previous three years. The AME will then decide if it warrants additional testing or review by the Office of Aeronautical Medicine (OAM). The FAA can also get this information via other methods (for example if your employer reported you or you are jailed for some kind of mental health disorder outburst).
Certain conditions are automatically disqualifying, such as psychosis, bipolar disorder, and severe personality disorder.
Employer Perspective
There are laws in the US protecting employees from being discriminated against for mental health issues. Many companies have reporting and monitoring programs that assist a pilot with a psychological issue to seek help and get back to flying. The FAA participates in these programs and provides a "rigorous evaluation" before allowing the pilot to return to flying.
So from a commercial service perspective it is important to be open about the issues upfront and early, especially with your AME. Pilots have been arrested for denying mental health history.

Great answer, thank you very much. Your story feels frustrating... I hope they become less strict in the future. Although the current rules err to the side of caution, it seems too much.


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You are a commercial airline pilot flying between two large US airports. Who do you talk to along the way on the radio and for what purpose?
I am a non-pilot who has been listening to various ATC feeds and trying to understand what is going on. I've been able to find surprisingly little information on the various layers that make up the air traffic management system but from listening to SFO atc feeds online, I've come up with the following outline of what radio contacts on a domestic US flight would look like:

ramp control - I know it exists, but have little idea what they do. I would think they manage push back requests, but I hear that on ground frequencies so that cant be strictly correct.
ground control - request pushback, get taxi instructions and hand off to tower when near runway
tower - get takeoff clearance. hand off to departure during climb out
departure - request bearing and altitude, receive vector out of departure airspace in proper direction
center controller (various) - not sure what the relationship is here (pilot requests bearing, altitude, or is it all automated and known to controller) controller maintains separation mins.
approach - there seem to be two stages here? One controller asks for intentions, gives a waypoint and altimeter data. A hand-off is then done to another approach controller who vectors traffic into the pattern for landing, calls base, etc.
tower (arrival) - everything should be all spaced out, so controller just works on fitting departures in. Announce your intention and be granted clearance with initial taxi instructions.
ground (arrival) - get further taxi instructions to gate.

So how accurate is my picture of whats going on? I'd be interested to know exactly how the whole process works from the pilot's perspective. Some specific questions about the process:

How automated are aspects? Do controllers ever have information from filed flight plans or is all info passed over radio?
Whats the deal with the two approach controllers? (BSR2/MOD2 versus landing)

One of the ones you are missing is Clearance Delivery for ATC clearances prior to departure.

This is a duplicate question, although this is actually asked much better than the other one is.
Generally, your picture of what goes on is pretty good.
As mentioned in a comment, there is Clearance Delivery, which issues your ATC (IFR) clearance.  Except... at most of the larger airports, that function is now automated and the clearance is passed via ACARS, which is essentially a closed e-mail system direct to the aircraft.  So it's actually common to NOT talk to Clearance Delivery now in airline operations.  You still do at smaller airports that don't have the PDC (Pre-Departure Clearance -- the automation that sends the clearance itself over the ACARS network) installed, and you'll call Clearance if you have a question about how you were cleared, and in a few other uncommon situations such as a reroute that's issued after you got your initial clearance.
Ramp Control exists at some airports, and it's essentially a "ground control" function for a separate, isolated area.  So in Atlanta, you actually have several of these, one for Ramp 1, which is the east side of the A terminal and the west side of the B terminal, another for Ramp 2 which is the west B gates and the east C gates, and so on.  They control the "in's" and "out's" of their respective ramps, including coordinating who will push back when.  As the aircraft leaves the Ramp Control area, it's handed off to Ground Control, and things proceed normally.  NOT all airports have this, and not necessarily every terminal (or gate) at a given airport will be controlled by Ramp Control.  Gates that aren't controlled by Ramp will typically call Ground to push.  SFO is like this.
Typically, controllers see most of what you've filed on your flight plan, so they know before a given flight is passed to them that SkyPig 23 is a 757 that departed JFK, is filed for FL 360, and is going to ATL with a routing of whatever set of airways, points, and STAR.  NOT every controller will see everything in the flightplan; I think the TRACON sees remarks but the Center may not, was one example I vaguely remember from a tour a while back.  But essentially they know who you are & what you're doing by the time you switch to their frequency.  Sometimes things get confused or the pilot requests a change (in altitude, routing, or whatever), and sometimes the controller has to change the plan up, but generally you check in at whatever altitude (and climbing/descending to whatever, if that's the case) and the controller acknowledges and that's that until he has a new clearance (further climb or descent, new routing, approach clearance, etc) to issue.
Mostly now, airlines are filed on both a SID (standard instrument departure) and a STAR (standard terminal arrival route) so  "requesting vectors" in pretty uncommon.  Could happen if your FMC (flight management computer) dumps your routing, but that's rare, and usually operator error when it does happen.  A departure or an arrival might INCLUDE vectors (i.e. fly heading 350, climb & maintain 5000', expect radar vectors to JEBBB), but in those cases it's expected.
Multiple approach controllers are pretty common, especially in the larger terminal areas.  Often you'll be switched from Center to one Approach Control frequency, who may be handling all arrivals from the east, with another handling everything from the west.  Then as you get close to the airport, they hand you off to "Final", which is still "XYZ Approach" but his job is sequencing everybody onto the base, dogleg, and final, clearing you for the approach, and then handing you off to tower.  If the first Approach controller owns airport to 30NM out surface to 17,000', the "Final" controller might own 7000' and below within 12 miles, and Tower owns 3000' and 5 miles.  Serious generalization there, but that's the idea... each successive layer of the onion owns a smaller but busier piece of airspace.  Letters of Agreement between the Center and the TRACON and then procedures within the TRACON will spell things out in great detail.
Hope that's helpful.  Good question asked well; hopefully this won't be lost to memory just because it was asked 2nd.


text:
How many airport charts do airline pilots have in the cockpit?
I always wonder how many "backup" approach charts and airport diagrams airline pilots have in case the plane has to divert. I imagine a few possibilities:

There are no approach charts in the cockpit. The only ones the pilots have are those with the flight plan: the departure, destination and any alternates they picked along the route. If the plane must land somewhere else, the pilots will ask ATC to guide them in.
All of the fleet's destinations are available in the cockpit. If the plane diverts to any one of these airports, it is likely that there will be a ground crew to serve the passengers.
Every airport that can accommodate the size of the airplane is available, irrespective of whether it is a destination of one of the airline's routes.
Every airport within the operation area, no matter how big or small, is available.

I imagine with more airlines using Electronic Flight Bags, this would be a non-issue as one can easily load all available charts in the world onto the tablet, and updating them is trivial. Still I am interested in knowing what airlines typically do.

In the 1990s I flew for two 747 carriers, the first primarily a freight carrier and the second primarily a passenger carrier. Both used Jeppesen for their airway manuals, and both supplied each pilot with a single, full-size and very full Jepp manual that contained as many as possible of the airports we might go into. Image below:

As I remember, the criteria for whether a plate would be in our personal binder included the airport having a runway at least 5000 feet long.
Both carriers did extensive charter work to every continent save Antarctica, and we would occasionally be dispatched to an airport that our personal Jepp manual didn't have. The freight carrier handled this problem by having aboard each aircraft a flight bag with full, world-wide coverage, 5 or 6 manuals as I remember. In theory the manuals were kept current by updating them each time the aircraft went through its base, but in practice they were almost always out of date, but at least they were there in case of an inflight diversion to an unplanned airport.
The pax carrier handled the problem of an airport not in our personal coverage by faxing the plates with our flight plans. In case of an unplanned inflight diversion, dispatch would read the pertinent information to us over HF, a very tedious procedure, obviously. I only had that happen once.
It was a different world back then with no ubiquitous Internet. I typically spent 300 to 400 dollars per month in international phone calls to my wife. No Skype, no WhatsApp, Compuserve for email until around 1996 or so, then sporadic Internet, but always dial-up and with ridiculous charges by the hotels.

The major international carrier I‘m most familiar with used to, in the olden days, carry charts for all airfields in the area of operation for that particular aircraft type that were deemed useable by the operations department for that type. There is a team and process for performing the required airfield assessments.
Nowadays on the EFB, this airline’s pilots have access to charts for all airfields any of that airline‘s aircraft types are allowed to use, and they also have a means of seeing how suitable the operations department deems any particular one of these airfields for that particular aircraft type.

It's going to depend on the air carrier, but in the EFB age there isn't much of an economic advantage to curtailing your Jepp subscription. A US Pt.121 Flag or Domestic airline will have a list of approved airports they can "plan" from (including enroute diverts, like ETOPS), but in an emergency they can go anywhere.


text:
Would cone shapes grills in front of jet engines prevent damage in case of a bird strike?
If cone shaped grills pointing forward were in front of jet engines would they make bird parts slide outside towards the back of the engine and away?

Would they immensely affect the drag and efficiency of the engines? Would they serve in any way to better help the plane fly safely and controllably?

Duplicate of http://aviation.stackexchange.com/q/14342/8730

No, that wouldn't work.
Kinetic energy is measured using the formula $\tfrac12mv^2$ . This means that the kinetic energy of a 4.5kg goose at 170 knots is about the same as a motorcycle at 30mph. At 400 knots that goose's kinetic energy is the same as a small car at 30mph. Remember that velocity in this case is not the speed of the goose but the speed of the airplane hitting it, any grill would have to be immensely strong to survive that kind of impact, meaning it would have to be thick and heavy. This will block airflow to the engine, which is a big problem. If the heavy, hard metal screen fails it will get sucked into the engine and cause far more damage than a soft, squishy bird.
One method for the mass production of french fries is to shoot potatoes at a mesh screen at high speed using a water cannon, when the potato hits the screen its speed forces it through, slicing the potato perfectly in a fraction of a second. A similar thing is going to happen to a bird which hits a screen in front of the engine, rather than being deflected it will simply be sliced and ingested into the engine anyway, or it could potentially be caught on the mesh of the grill and impede airflow further.

Chicken strips.

Jet engine crispy duck. Yum.

Sheer genius @mins

That would hinder the engines so much that they probably wouldn't create enough thrust to maintain level flight.


text:
Are jet engines affected by small bird (e.g. hummingbird) strikes?
If a hummingbird got sucked into a commercial jet engine at takeoff would the pilot notice? This is a serious question.

No, you probably wouldn't notice at all. If the bird went into the engine core, you might have a slight smell in the airconditioning system of burnt bird, but that's it. See these two answers for more details: birdstrikes and birdstrikes on landing.

"...to show we can sustain operation after ingesting a bird carcass"

Serious, as in: does the pilot start humming a tune? Sorry. Does the info in this question help?

All turbine engines must pass a series of tests, including water ingestion (flying through clouds) and bird strikes. For bird strikes, the following article does a good job explaining the requirements to pass bird strike testing:
Aircraft Certification for Bird Strike Risk
It cites 14 CFR Part 33-77 'Foreign object ingestion - ice' (although 14 CFR Part 33-76 'Bird ingestion' seems more appropriate) and EASA Airworthiness Code CS-E 800 'Bird Strike and Ingestion' as sources.
14 CFR Part 33-76:

(4) A small bird ingestion test is not required if the prescribed number of medium birds pass into the engine rotor blades during the medium bird test.
(5) Small bird ingestion tests shall be conducted so as to simulate a flock encounter using one 85 gram (0.187 lb.) bird for each 0.032 square-meter (49.6 square-inches) of inlet area, or fraction thereof, up to a maximum of 16 birds. The birds will be aimed so as to account for any critical exposed locations on the first stage rotor blades, with any remaining birds evenly distributed over the engine face area.
(6) Ingestion of small and medium birds tested under the conditions prescribed in this paragraph may not cause any of the following:

More than a sustained 25-percent power or thrust loss;

The engine to be shut down during the required run-on demonstration prescribed in paragraphs (c)(7) or (c)(8) of this section;
The conditions defined in paragraph (b)(3) of this section.
Unacceptable deterioration of engine handling characteristics

EASA Airworthiness Code CS-E 800

(d) Medium and small birds ingestion tests. Engine ingestion tests and analysis with medium and small sized birds must be carried out as specified below. Alternative evidence may be acceptable as provided under CS-E 800 (f)(1). The small birds test will not be required if the prescribed number of medium birds pass into the Engine rotor blades during the medium bird test.
(B) Small birds. One 85 g bird for each 0·032 m2 of the inlet throat area or fraction thereof with a maximum of 16 birds, distributed to take account of any critical exposed

For more information, refer to 14 CFR Part 33-76, and EASA Airworthiness code CS-E 800.
One more thing to add - the documents do not include any tests for single small birds, only flocking small birds, and use birds that weigh 85 grams. Humming birds do not flock, and 85g is more than most humming birds weigh. That being said, the tests do include much larger birds, and all commercial jet engines found on commercial airlines certify large bird strikes, so it's likely that tests with small bird strikes are not conducted. Bouncing off of physics - if a turbine can withstand a large bird strike, it won't even feel a humming bird strike, therefore it is not a required test if the engine already certified with large bird strikes.

Including some salient points from the linked article would help, just in case the link goes dead. It's a bit of a tradition 'round these parts.

Done. There's quite a bit of information in the CFR and EASA, including lots of tables and numbers. For more information, it's best to just read those documents.

It seems I was editing while you did that, so your edit was overwritten by mine. I'll add the quotes

Fair enough! No worries.


text:
What does the ACARS Weight and Balance Request page look like?
In the ATSU AOC Preflight menu of an Airbus (maybe Boeing too), there is an option for a weight and balance request. The selection name varies by airline but it may say "W/B Req" "Send LoadSheet" "LoadSheet REQ & Confirm" "Weight Manifest Request" "Loadsheet Request" "Load Data Report" or "W/T Balance".
What does this page look like? What information does the pilot have to enter in this page?

As you said, it will vary by airline. Mine has a few screens, and the pilots enter in number adults and children in each seating zone, number of total infants, number of standard and heavy items in cargo, any additional weight in cargo (shipping cargo, mail, ballast, etc). Also the desired runways to get data for and their condition (dry, wet, snow, etc).
Many, sometimes all, of these items are auto-populated when the gate agent closes the flight, except for the desired runways.
When the response is received, it contains weights and center of gravity numbers, and then each runway will have specific thrust (temperature, ECS/bleeds, flex, and target resulting thrust) and flap settings, as well as the V speeds.

"When the response is received, it contains weights and center of gravity numbers," Doesn't this already come from the loadsheet that is delivered via ACARS after loading is complete? Is the pilot filling the weight and balance request after receiving that final loadsheet?

Varies by airline, my answer is mostly specific to mine. We don't get a distinct load sheet through ACARS. Our takeoff data request is automatically populated with passenger and baggage/cargo counts, and then we send for the takeoff data. This calculates everything and sends a takeoff report back to us that includes everything my answer outlines.


text:
What airfoil parameter should I focus on to achieve the maximum service ceiling?
I am working on a design competition project where I have to design a low subsonic aircraft for high altitude performance.
From what I have studied service ceiling will depend on excess power available so I should focus on minimising drag or minimising cl/cd.
Problem is I haven't seen any aircraft in service that uses high lift airfoils, why is it so? What parameter should I focus on to design a better wing?

Some information about the aircraft and the constraints set by the rules of the competition:
The aircraft has a 3.5 metre wingspan, weighing in the ballpark of 25 kg, although maximum weight allowed is 50 kgs. It has to carry 5 kg payload to >6000m altitude on electric propulsion.

This question is much too broad. What constraints do you have? What is your approximate target altitude?

The wingspan is defined by the competition parameters? I would suggest looking at semi-symmetrical or under-cambered airfoils for best lift performance.

What's the max speed? Mission profile? General configuration?

Given that you must use electric propulsion and have a size constraint, the usual criterium of selecting for the maximum product of lift coefficient and flight Mach squared will not apply here. Instead, this can be dealt with using incompressible aerodynamics.
Therefore, the figure of merit is to maximize $\frac{c_L^3}{c_D^2}$ in order to stay airborne with the smallest possible power. Given that you not only need to lift your airplane's mass up but also need to accelerate it so dynamic pressure can stay constant, you will achieve the highest altitude when you can make most of the limited energy stored at take-off.
Since induced drag at the optimum operating point will be three quarters of total drag and span is limited, you need to save mass where ever you can. This includes the selection of a capable airfoil because a thick wing and a high lift coefficient will improve structural efficiency and reduce wing area. However, make sure to use all the mass allowance to pack as much battery capacity as possible. If the rules allow, consider dropping empty battery packs enroute.
Without having performed an exhaustive comparison, I would start with the Daedalus airfoil set (DAE-11 at the root to DAE-31 at the tip) and adapt those to the Reynolds numbers you will meet in flight.

Don't worry about the airfoil at the start.  You need to focus first on getting the wing area right.
Do you have a speed requirement at altitude?  For example, do you have to be able to maintain a spot over the ground in some expected headwind?
Your airplane will fly at CL=W/(q*S).
q=0.5rhoV^2 is determined by your flight condition.  If you are free to choose V, then things are more complex.
You want to fly at CL for best L/D.  For a given drag polar, that is a specific value of CL.
If you know your target CL, flight condition, and weight -- you can solve for the wing area S that will make it happen.
You want as much span as you can get -- do you have a span constraint?  If not, you will be limited by structures.  Keeping S constant, increasing span will shrink the chord and also the thickness of the airfoil.  Such a thin spindly wing will not support the load.
Once you know chord and flight condition, you will know the cruise Reynolds number.  You also know the cruise lift coefficient.  For a straight, high aspect ratio wing, your sectional lift coefficient will be close to the cruise lift coefficient.  You should start by selecting an airfoil with a design cl that matches your cruise CL.
This process is iterative -- you make a guess about the drag polar, calculate  everything through, and then update your drag polar estimate based on the real wing area, the airfoil selected, etc.  Then iterate again.  A few times through and you'll converge on a good wing loading and airfoil for your point.


text:
Does my instrument rating 250NM cross-country also count for my 100NM commercial one?
Can the 250NM XC required for the instrument rating per 61.65(d)(iii)(A) also count for the 100NM day dual commercial XC required in 61.129(3)(iii)?
My 250NM XC during instrument training included a leg that exceeded 100NM from the departure field. Simply put: have people been able to get away with "double dipping" on this requirement? I read a LOI stating that you couldn't apply requirements for a certificate while pursuing another certificate.
However, an instrument rating is a rating, NOT a certificate.

It appears that you can do that, because you would be using a portion of training with specific requirements to comply with another training with general requirements. The LOI appears to state that's ok, but the opposite is not.

The wording DAY VFR was removed from the 61.129(a)(3)(iii) regulation in October 2009.  I was about to respond that I was told it needed to be day VFR but since I did that requirement the regulation has changed.

First, see this question for some extra context. As a general statement, you can use instrument training to count towards commercial training, but only if you can demonstrate that it met the commercial requirements.
If you look at the commercial XC requirements, you can see it explicitly requires that the training has to be to commercial standards:

(3) 20 hours of training on the areas of operation listed in
§61.127(b)(1) of this part that includes at least
[...]
(iii) One 2-hour cross country flight in a single engine airplane in
daytime conditions that consists of a total straight-line distance of
more than 100 nautical miles from the original point of departure;

So what does that mean for you? Well, if you can prove that your IR XC training was to commercial standards then you can double dip it. Perhaps you're at a flight school that deliberately plans and documents things that way. Or your IR instructor is willing to endorse your logbook with the remark that the IR XC was conducted to commercial standards.
On the other hand, if you did your instrument rating ten years ago and only started working on your commercial recently, it would probably be tough to "provide evidence" (as the FAA puts it) that your IR XC was indeed to commercial standards.
You could ask the DPE who'll do your checkride what they're looking for, although that draws attention to the question and you might not know which DPE you'll use. So all in all, if there's any doubt about whether your IR XC was to commercial standards, the simplest thing is simply to go fly a new, commercial XC with your instructor.

How might an IFR cross country flight performed 10 years prior NOT conform to "commercial standards" by virtue of elapsed time?  If the origin and destination are logged, the distance can easily be determined at any time.

When you say "commercial standards," do you mean the list of topics in §61.127(b)(1)? These are almost identical to the list of topics for the private in §61.107(b)(1) so I'm not sure where you're getting the idea that "it explicitly requires that the training has to be to commercial standards."

There doesn't appear to be anything in the regulation that says you can't double dip. The Theriault interpretation you linked to implies you can't, but it doesn't provide a source for that beyond just "see §61.127."
The Pratt interpretation explicitly rescinds that interpretation for being wrong anyway (albeit wrong in a different way), so it's not clear that there is any statement from the FAA still in force that they believe you can't double dip even with certificates.
Still, despite there being nothing saying you can't, there's not really anything you could point a DPE to to show you can, so it's probably wiser to not to so I'm case your DPE doesn't like it.
§61.127 does say that the training needs to be done on the topics listed in §61.127(b), but that shares topics with §61.65(c) for an instrument rating, so there's no reason you can't do both at the same time.
Though if you did your IR XC with a CFI-I who doesn't have their CFI-A, I suppose they wouldn't count as an "authorized instructor" for the purposes of the commercial training, which may or may not cause it not to count.

I don't thing the term "double dipping" is even appropriate in this context:  If you applied for two jobs, both of which require a bachelor's degree, would you be required to have two bachelor's degrees? Of course not.
Now, if there was a required progression from commercial to instrument, (or vice versa) it would be logical to presume that the requirements are cumulative...  or that one is a prerequisite for the other.  In other words, you need to fly a >250/100nm X-country to get your commercial, commercial is required before instrument, and for instrument you also need a >250/100nm X-country, therefore you need two total.
However, this is not the case.  A Commercial Pilot Certificate and an Instrument Rating are completely separate and independent things.  You can have either without the other.
Regulations are generally restrictive, not permissive.  In the absence of a specific regulation stating that the requirements for each cannot be met by by the same event, it should be presumed that a single X-country flight that meets the requirements for both may be counted for either.


text:
How to obtain transformation parameters between the Vertical Reference System EGM-96 and a Local Geoid Model?
Dear Mr/Mrs Geodesy Engineer, Cartographers and AIS Specialists
I have a quite deep question here,
AIP data locations are determined by geographic coordinates /X & Y axis/ and vertical values /Z axis/ via Geodesy science.
ICAO adopted EGM-96 standard for Vertical Reference System.
Question is raised regarding to Annex-15, 1.2.2.3:

....When a geoid model other than the EGM-96 model is used, a
  description of the model used, including the parameters required for
  height transformation between the model and EGM-96, shall be provided
  in the Aeronautical Information Publication (AIP).

In Mongolia, we are not using EGM-96 for Vertical Reference System. Instead, wWe are using the Baltic sea level value /1940-1970/ in Air Navigation.
My question is: How to figure out the parameters required for height transformation between any model and EGM-96 for AIP publication?
In my thinking, the parameters must contain following values: ∆X, ∆ Y, ∆ Z, X rotation, Y rotation, Z rotation, Scale... etc. Is this correct?

Interesting question, and I think it is on topic. However, I would expect this question will get better answers at https://gis.stackexchange.com/,

The few thousand different projections that exist and transforming between them is a problem GIS professionals deal a lot more frequently than pilots. As @DeltaLima has suggested, you're much more likely to get a good answer at gis.stackexchange.com.